Contingencies and Regulatory Matters - Recovery Balance of Each Regulatory Clause - Gulf Power (Details) - GULF POWER CO - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other regulatory liabilities, current
Loss Contingencies [Line Items]
Fuel Cost Recovery	$ 0	$ 15
Over recovered regulatory clause revenues
Loss Contingencies [Line Items]
Fuel Cost Recovery	7	0
Purchased Power Capacity Recovery	5	0
Environmental Cost Recovery	12	13
Energy Conservation Cost Recovery	$ 2	$ 4